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I have a 2001 F150 with the 4.6 engine. I replaced the thermostat and the blend door IS working properly, and I flushed the heater core and I still have no heat. What else could this be?
Between 10-15 minutes the inlet and outlet hose gets very hot to the touch, and I’ve noticed when I drive with both heat and air off and I turn it on heat it will blow a rush off hot air but then it gets back cold
and I’ve noticed when I drive with both heat and air off and I turn it on heat it will blow a rush off hot air but then it gets back cold
At that point and with the blower still on high, check the temperature of the hoses.
Your basic symptom is of insufficient hot coolant in or passing through the core. Turning off the blower allows it to accumulate in the core and plenum. You need to determine whether or not here is a very substantial drop in the temperature of the outlet.
So should I try flushing the heater core back out again? If the temp on the outlet hose decreases after the rush of hot air?
Like projectSHO89 said above, you need to feel the hoses again after the initial blast of heat goes away and the air gets cool again. If one hose is hot and the other cold you have a blockage in the heater core. If both are hot you have a blend door issue or scale build-up on the inside of the heater core.